Fix #502

(cherry picked from commit e2fb2ab1e2b5925f16d4dd5c3ac514a0e54ee026)

Conflicts:
	framework/Web/Javascripts/source/prado/controls/slider.js

1 files changed, 21 insertions, 10 deletions

diff --git a/framework/Web/Javascripts/source/prado/controls/slider.js b/framework/Web/Javascripts/source/prado/controls/slider.js
index 2e26ee51..d612d654 100644
--- a/framework/Web/Javascripts/source/prado/controls/slider.js
+++ b/framework/Web/Javascripts/source/prado/controls/slider.js
@@ -18,17 +18,9 @@ Prado.WebUI.TSlider = Class.extend(Prado.WebUI.PostBackControl,
 		this.maximum   = this.options.maximum || this.range.end;
 		this.minimum   = this.options.minimum || this.range.start;
 		this.hiddenField=$(this.options.ID+'_1');
+		this.trackInitialized=false;
 		
-		// Will be used to align the handle onto the track, if necessary
-		this.alignX = parseInt(this.options.alignX || - this.track.offsetLeft);
-		this.alignY = parseInt(this.options.alignY || - this.track.offsetTop);
-		
-		this.trackLength = this.maximumOffset() - this.minimumOffset();
-		this.handleLength = this.isVertical() ? 
-			(this.handle.offsetHeight != 0 ? 
-				this.handle.offsetHeight : this.handles.style.height.replace(/px$/,"")) : 
-				(this.handle.offsetWidth != 0 ? this.handle.offsetWidth : 
-					this.handle.style.width.replace(/px$/,""));
+		this.initializeTrack();
 	
 		this.active   = false;
 		this.dragging = false;
@@ -64,6 +56,24 @@ Prado.WebUI.TSlider = Class.extend(Prado.WebUI.PostBackControl,
 		if(this.options['AutoPostBack']==true)
 			this.observe(this.hiddenField, "change", Prado.PostBack.bindEvent(this,options));
     
+	initializeTrack : function()
+	{
+		if(this.trackInitialized || !$(this.track).is(":visible"))
+			return;
+
+		// Will be used to align the handle onto the track, if necessary
+		this.alignX = parseInt(this.options.alignX || - this.track.offsetLeft);
+		this.alignY = parseInt(this.options.alignY || - this.track.offsetTop);
+
+		this.trackLength = this.maximumOffset() - this.minimumOffset();
+		this.handleLength = this.isVertical() ?
+			(this.handle.offsetHeight != 0 ?
+				this.handle.offsetHeight : this.handles.style.height.replace(/px$/,"")) :
+				(this.handle.offsetWidth != 0 ? this.handle.offsetWidth :
+					this.handle.style.width.replace(/px$/,""));
+		this.trackInitialized=true;
+	},
+
 	},
   
 	setDisabled: function(){
@@ -151,6 +161,7 @@ Prado.WebUI.TSlider = Class.extend(Prado.WebUI.PostBackControl,
 	
 	startDrag: function(event) {
 		if(Event.isLeftClick(event)) {
+			this.initializeTrack();
 			if(!this.disabled){
 				this.active = true;
 				var handle = Event.element(event);